The Universal Mobile Telecommunication System (UMTS) is one of the third generation mobile communication technologies designed to succeed the Global System for Mobile communications (GSM). Long Term Evolution (LTE) is a project within the 3rd Generation Partnership Project (3GPP) to improve the UMTS standard to cope with future requirements in terms of improved services such as higher data rates, improved efficiency, and lowered costs. The Universal Terrestrial Radio Access Network (UTRAN) is the radio access network of a UMTS and Evolved UTRAN (E-UTRAN) is the radio access network of an LTE system. In an E-UTRAN, a wireless device such as a User Equipment (UE) 150a is wirelessly connected to a base station (BS) 110a commonly referred to as an evolved NodeB (eNodeB), as illustrated in FIG. 1. Each eNodeB 110a-b serves a certain area which may be referred to as a cell 120a-b. 
In a wireless communication system using a frequency divisional multiplexing technology such as the Orthogonal Frequency Division Multiplexing (OFDM) technology, the entire channel is divided into many narrow sub-channels, which are transmitted in parallel. The OFDM technique transforms a frequency selective wide-band channel into a group of non-selective narrowband channels, making the channel robust against large delay spread by preserving the orthogonality in the frequency domain. The primary advantage of OFDM over single-carrier schemes is its ability to cope with severe channel conditions without complex equalization filters in the receiver. Channel equalization is simplified because OFDM may be viewed as using many slowly-modulated narrowband signals rather than one rapidly-modulated wideband signal. The low symbol rate makes the use of a guard interval between symbols affordable, making it possible to handle time-spreading and eliminate inter-symbol interference.
In an LTE system the OFDM-based technology is adopted as a mean to achieve high transmission capability and robustness to multi-path delay. Orthogonal Frequency-Division Multiple Access (OFDMA) is used in the downlink, and Single-carrier frequency-division multiple access (SC-FDMA) is used in the uplink. OFDMA is a multi-user version of OFDM, where multiple access is achieved by assigning subsets of sub-carriers to individual users. SC-FDMA is a linearly pre-coded OFDMA scheme. The distinguishing feature of SC-FDMA is that it leads to a single-carrier transmit signal, in contrast to OFDMA which is a multi-carrier transmission scheme.
Channel estimation has been widely used to improve the performance of OFDM systems, and is crucial for e.g. coherent demodulation which assumes channel knowledge at the receiver. It is also used in multi antenna systems to increase the throughput or coverage using transmission or receive schemes that require channel knowledge at the transmitter and/or receiver. Pilot based channel estimation schemes are commonly used. In such a scheme known reference symbols—also called pilot symbols—are inserted at regular intervals in the time-frequency grid. Using the knowledge of the pilot symbols, the receiver can estimate the frequency domain channel around the location of the pilot symbol. The channel's frequency response across the whole bandwidth can thus be determined by interpolation using various channel estimation schemes, such as Least Square (LS), Linear Minimum Mean Square Error (LMMSE), Discrete Fourier Transform (DFT), or Discrete Cosine Transform (DCT) based estimation. Channel estimation is affected by the channel conditions such as Signal to Noise Ratio (SNR), mobile velocity and multi-path delay spread.
There is therefore a need to improve channel estimation in communications system applying frequency division multiplexing.